An improved particle spray apparatus and method is used to electrostatically charge particles entrained in a flow of air and to direct the flow of air and particles toward a workpiece.
A known apparatus for directing a flow of air with electrostatically charged particles entrained therein toward a workpiece is disclosed in U.S. Pat. No. 4,819,879. This apparatus includes a spray gun having a central passage along which a flow of air with particles entrained therein is conducted. The flow of air with particles entrained therein is radially expanded by engagement with a conical deflector.
The apparatus disclosed in the aforementioned U.S. patent includes an electrical apparatus which electrostatically charges the particles entrained in the flow of air. The electrical apparatus includes various electrode arrangements which are exposed to the flow of air and particles around an axially outer end portion of the deflector. The electrode arrangement may include a silicon carbide electrode sheet which is mounted on the axially outer end portion of the deflector.
Another known particle spray gun is disclosed in U.S. Pat. No. 3,964,683. The particle spray gun disclosed in this patent includes a nozzle in which an electrode support member is mounted. A needle-shaped charging electrode is disposed in a passage which extends through the support member. Air is conducted to the passage in which the electrode is disposed to blow powder off of the electrode. The air is conducted through a passage in a radially extending spoke or strut which supports the support member in the nozzle.